Cancer remains a formidable disease with a high mortality rate in today's society. Indeed, cancer is second only to cardiovascular disease as a cause of death, killing one out of four people in developed countries.
Cancerous tumors commonly originate from normal cells which transform into malignant cells or tumors. The initial tumor growth may be slow and thus may be difficult to detect. The growth often becomes more aggressive and invasive with time, eventually spreading throughout the whole body and resulting in death.
Cancer treatment usually includes immunotherapy, surgery, radiation, hormones, and chemotherapy. In the past forty years, cancer chemotherapy has truly revolutionized the treatment of malignant tumors. Curative treatment has been discovered for many of the cancers that affect children and young adults, including acute lymphocytic leukemia, Hodgkin's disease, testicular carcinoma, and many others. However, despite being a powerful method of treating cancer, chemotherapy does suffer from a few problems. The most prominent problem is the low specificity of the anticancer agents. That is, most anticancer agents do not adequately distinguish normal cells from cancer cells. As a result, they often carry undesirable serious side effects. Such limitations of conventional chemotherapies underscore the urgent need for new anticancer agents with high antitumor activities and specificity to the cancerous cells.